I'm told that the rules regarding the 'tipping' thing differ between tipping someone up and then hanging on to them as you lower them to the ground or doing what Warburton did and just letting the player drop. I'm not saying that it was malicious, I'm sure it wasn't, but the bloke could have broken his neck.
exactly how I saw it Avalon and I'm not surprised he was pinged then sent off for it 
I remember Brian O'Driscoll being on the receiving end of a similar tackle in a Lions match a couple of years ago, Pengy, (against the All Blacks, I think) only there was more than a hint of malice in that one. O'Driscoll got a nasty injury and, as a result, there was such an outcry about 'spear tackles' that the refs were told to exercise zero tolerance regarding them.